Thanks. Turns out it's not as impressive on brass pressure fittings as on generic steel bolts/nuts. Maybe because the threads fit tighter to start with? I had to let it soak in for a couple hours and 2-3 shots of PB before I could get the fittings loose but it did eventually work on all but one.
Here's a tip: avoid using this stuff indoors if possible, since the smell "penetrates" the house just as much as the liquid penetrates the threads.
I never heard of Kroil before. Thanks for pointing it out. Kinda pricey, and like you said it's a bit hard to find. Might have to try the ATF and acetone sometime.